Modifiers matching grump:

• greedy,
• wealthy,
• gruff,
• covetous,
• grouchy,
• heartless,
• grizzled,
• rich,
• arrogant,
• misanthropic,
• ill-tempered,
• fastidious,
• impatient,
• jealous,
• miserly,
• mean,
• principled,
• condescending,
• penny-pinching,

Simple categories matching gruff:

• policeman,
• warrior,
• hacker,
• tyrant,
• person,
• adventurer,
• outdoorsman,
• actor,
• thug,
• spy,
• pioneer,
• soldier,
• hero,
• president,
• bully,
• explorer,
• robot,
• cop,
• pianist,
• convict,
• boxer,
• demon,
• cowboy,
• criminal,
• grump,
• director,
• thief,
• superhero,